双向链表

*ListNode 比单向多一个pre指针

*部分方法细节修改

package LeetcodeExercise;

public class DoubleLinkedListTest {
    public static void main(String[] args) {

    }
}

class DoubleLinkedList{
    private ListNode2 head = new ListNode2(0," ");//head不能动

    public ListNode2 getHead() {
        return head;
    }

    //遍历
    public void list(){
        if(isEmpty()){
            return;
        }
        ListNode2 temp = head.next;
        while (true){
            if(temp == null){
                break;
            }
            System.out.println(temp);
            temp = temp.next;
        }

    }

    public boolean isEmpty(){
        if(head.next == null){
            System.out.println("空链表");
            return true;
        }
        return false;
    }

    public void insertNodeTail(ListNode2 listNode){
        ListNode2 temp = head;
        while (true){
            if(temp.next == null){
                break;
            }
            temp = temp.next;
        }
        temp.next = listNode;
        listNode.pre = temp;//和单链表不同
    }

    public void updateNode(ListNode2 listNode){
        if(isEmpty()){
            return;
        }
        ListNode2 temp = head.next;
        boolean flag = false;
        while (true){
            if(temp == null) {
                break;
            }
            if(temp.no == listNode.no){
                flag = true;
                break;
            }
            temp = temp.next;
        }
        if(flag){
            temp.value = listNode.value;
        }else {
            System.out.println("no listnode.no like this!");
        }
    }

    public void deleteNode(int no){ //和单链表不同
        if(isEmpty()){
            return;
        }
        ListNode2 temp = head.next; //是需要删除的结点
        boolean flag = false;
        while (true){
            if(temp == null) {
                break;
            }
            if(temp.no == no){
                flag = true;
                break;
            }
            temp = temp.next;
        }

        if(flag){
            temp.pre.next = temp.next;
            if(temp.next != null) {
                temp.next.pre = temp.pre;
            }
        }else {
            System.out.println("no listnode.no like this!");
        }


    }



}


class ListNode2{

    int no;
    String value;
    ListNode2 next;
    ListNode2 pre;
    public ListNode2(int no, String value) {
        this.no = no;
        this.value = value;
    }

    @Override
    public String toString() {
        return "ListNode{" +
                "no=" + no +
                ", value=" + value +
                '}';
    }
}